Lubricant containing a phosphorus acid ester-aldehyde condensation product



United States Patent LUBRICANT CONTAINING A PHOSPHORUS ACID ESTER-ALDEHYDE CONDENSATION PRODUCT John R. Morris, Fishliill, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Original application August 22, 1950, Se-

rial No. 180,901. Divided and this application July 24, 1952, Serial No. 300,757

3 Claims. (Cl. 252--46.6)

This invention relates to lubricating compositions containing compounds selected from a new class of organic phosphorus compounds. More particularly it relates to lubricating compositions containing condensation products obtained by reacting phosphate partial esters with aldehydes.

This is a division of my copending application Serial No. 180,901, filed August 22, 1950.

It is old in the art to employ phosphate esters as addition agents in lubricating compositions to improve various characteristics of the lubricating compositions such as their resistance to oxidation, corrosiveness, detergency, oiliness, viscosity index and so forth. More recently, it has been found that phosphate esters containing sulfur in direct linkage with the phosphorus are particularly valuable modifying agents for lubricants, and a large number of such compounds have been used, chiefly as multifunctional additives for extreme pressure lubricants. For example it is disclosed in U. S. 2,242,260, to Prutton, that extreme pressure agents are produced by reacting phosphorus pentasulfide with various organic compounds including stearic acid, lauryl alcohol, benzyl alcohol, naphthenic acid, butyl stearate, phenol and chlorophenol. Extreme pressure agents are also prepared by the method of U. S. 2,396,719 to Musselman et al., whereby phosphorus pentasulfide is reacted with an alcohol. The reaction product is preferably further reacted with a base such as ammonia, an amine, or a metal oxide or hydroxide. U. S. 2,252,985 to Rutherford et al., discloses that the oxidation resistance of a lubricant is increased by the addition of alkaline earth metal salts of esters obtained by reacting aliphatic or aromatic alcohols or mercaptans with sulfur-containing acids of phosphorus. U. S. 2,470,405, to Leland, discloses that the load hearing quality of cutting oils is improved by the addition of esters having the formulas P(XR)3 and XP(XR)3, wherein X is either oxygen or sulfur, at least one R is hydrogen and the remaining Rs are aliphatic or aromatic hydrocarbon radicals. U. 8. 2,368,000, to Cook, discloses anti-foaming agents prepared by reacting phosphorus pentasulfide with branched chain alcohols and neutralizing the product with 'heavy metal salts. U. S. 2,343,831, to Osborne, discloses dialkyl and diaryl dithiophosphate polysulfides as extreme pressure agents. 7

While compounds of the above type are very effective in improving a number of lubricant properties, they also possess certain disadvantages which are more or less serious depending upon the purpose for which the lubricant is to be employed. The esters themselves are highly acidic and corrosive, so that they must usually be employed in the form of their salts or other compounds. However, many of these compounds heretofore proposed hydrolyze or otherwise decompose at high temperatures, and the use of metal salts is undesirable in many cases,

2,736,706 Patented Feb. 28, 1956 as for example where there are rigid restrictions upon the permissible amount of non-volatile ash remaining after combustion.

It is an obiect of the present invention to provide improved lubricants containing organic phosphorus compounds. Another object of the invention is to provide a novel class of multifunctional lubricant additives. Another object of the invention is to provide a class of compounds having the property of imparting improved lubricating characteristics to a lubricant composition without having undesirable or deleterious effects upon other properties of the lubricant composition.

The novel lubricant additives of my invention are the condensation products obtained by reacting partial esters and thio esters of phosphorus acids and thio acids of the types shown in the foregoing patents, with aldehydes. These compounds are preferably monomeric condensation'products which may be represented by the general formula RIX XRs wherein X is oxygen or sulfur, Y is either oxygen or sulfur or is absent, and R, R1, R2, R3 and R4 represent hydrogen or organic radicals which may be the same or different, at least one organic radical being attached to each phosphorus atom through an oxygen or a sulfur atom. The organic radicals may be aliphatic groups, including open chain and cyclic, saturated and unsaturated aliphatic groups, aromatic groups, or substituted aliphatic or aromatic groups. Sufiicient alkyl carbon atoms are contained in these organic groups to impart oil-solubility to the molecule. These organic groups may also contain any of the inorganic substituents commonly employed in lubricant additives, such as halogen atoms, hydroxyl groups, carboxyl groups, nitro groups, amino groups, mercaptan groups and so forth.

My preferred compounds for use as lubricant additives may be represented by the following formula S XRi wherein X is oxygen or sulfur, R is hydrogen or an organic group and R1, R2, R and R4 are organic groups as described above.

As specific examples of such compounds which are particularly suitable for use as lubricant additives are the following:

Addition agents of the above type have important advantages over the known types of phosphate ester additives, particularly in that they possess increased chemical stability and decreased acidity and corrosiveness and do not add to the non-volatile ash content of the lubricant. They are antioxidant and corrosion-inhibiting both when used alone and with other more corrosive additives.

The amount of these phosphorus compounds which may be added to lubricating oils may be varied depending upon the effect desired and upon the characteristics of the base oil. In general, small proportions, for example from 0.1% to and preferably from about 0.5% to about 2%, are employed. However, either greater or less amounts may be used if desired.

While the compounds of my invention are preferably the monomeric condensation products as shown in the formula, 21 certain amount of more or less polymeric products may be formed when monoesters are present in the reaction mixture, and such compounds are also included within the purview of this invention, since it is conceived that useful resins and high molecular weight products having pour point-reducing and other valuable properties may be obtained by this condensation reaction.

The esters used in preparing the condensation products of my invention may be one or more of the following types: mono-esters of phosphorous and phosphoric acids, diesters of phosphorous and phosphoric acids, mono-thio esters of phosphorous and phosphoric acids, di-thio esters of phosphorous and phosphoric acids, monoand di-esters of tri-thio phosphorous acids, monoand di-thio esters of tri-thio phosphorous acids, monoand di-esters of tetra-thio phosphoric acid, and monoand di-thio esters of tetra-thio phosphoric acids. Esters of the above types may be obtained by any of the familiar esterification reactions between an aliphatic or aromatic alcohol or mercaptan and an oxygen and/or sulfur-containing phosphorus acid, such as phosphorous acid, phosphoric acid, thio phosphorous acid, thio phosphoric acid, phosphorus pentoxide, or a phosphorus sulfide such as phosphorus pentasulfide, phosphorus trisulfide or phosphorus heptasulfide, or by other ester-forming reactions such as the reaction between a halogenated hydrocarbon and a phosphorus acid salt such as di-sodium hydrogen phosphate. Esters suitable for preparing the preferred compounds of my invention may be readily obtained by reacting an alcohol or a mercaptan with phosphorus pentasulfide. The reaction of an alcohol with phosphorus pentasulfide and the condensation of the ester obtained with an aldehyde take place according to the following equations:

wherein R is an organic group and R is an organic group or hydrogen.

The alcohols employed in the above reaction may be aliphatic alcohols, including straight or branched chain or cyclic alcohols, preferably those containing from about 4 to about carbon atoms in the molecule, aromatic alcohols, preferably alkylated aromatic alcohols, or heterocyclic alcohols and such alcohols containing substituent groups in so far as those do not interfere to any appreciable extent with the esterification on condensation reaction. Suitable alcohols which may be mentioned include CaHn amyl alcohol, octyl alcohol, cetyl alcohol, lauryl alcohol, stearyl alcohol, benzyl alcohol, phenyl ethyl alcohol, diamyl phenoxy ethanol, cyclohexanol, methyl cyclohexanol, terpineol, cardanol, phenol, naphthol, cresol, xylenol, chlorophenol, octyl phenol, diamyl phenol and hydroquinone. The corresponding mercaptans and thio phenols may be used in place of these alcohols. Instead of a single alcohol or mercaptan, mixtures of two or more different alcohols or mercaptans or mixtures of both alcohols and mercaptans may be employed in the esterification reaction in order to obtain mixed esters.

The aldehydes employed in the condensation reaction may likewise be aliphatic, aromatic or heterocyclic in character and may contain'substituent groups such as those mentioned above in so far as these do not interfere with the condensation reaction. Suitable aldehydes which maybe mentioned include formaldehyde, acetaldehyde, trichloroacetaldehyde, butyraldehyde, benzaldehyde, salicylaldehyde and furfural.

The condensation reaction is carried out by reacting a phosphate partial ester of the type described above, or a salt of the ester such as the sodium salt, with an aldehyde, preferably in an alcohol solution in the presence of hydrochloric acid. The molar ratio of phosphate esterzaldehyde employed in the reaction may range from about 2:1 to about 2:6. It is preferably about 2: l.

The following detailed procedure illustrates a method which may be used for preparing the compounds of my invention.

EXAMPLE A diamyl phenol-P255 reaction product was prepared by adding 96 g. of P285 slowly to a solution of 500 g. of diamyl phenol in 250 cc. of xylene, refluxing the reaction mixture for 3 hours and permitting it to stand until the reaction was complete. The solution was finally filtered and the solvent removed by stripping. 587 g. of reaction product was obtained having a neutralization number of 82.3. 560 g. of this product was dissolved in 860 cc. of absolute alcohol and 100 g. of aqueous formaldehyde (37% by weight) and 50 cc. of concentrated HCl added. Gaseous HCl was passed in and the reaction mixture refluxed for 3 hours. It was then cooled and shaken with 1 liter of water in a separatory funnel. After separation of the water layer the product remaining was dissolved in ether, the ether solution washed repeatedly with water and an aqueous salt solution until the washings were neutral to litmus and the ether finally removed by steam stripping. 544 g. of product was obtained having a specific gravity of 0.991 and a neutralization number of 23.8.

The value of this compound as a lubricant additive has been demonstrated by means of a special test which was designed to show the corrosiveness and oxidation stability of a lubricating oil under the bearing lubrication conditions existing in an internal combustion engine. In this test a lubricating oil at an elevated temperature is continuously circulated and recirculated over a bearing specimen in the presence of air and of catalytic metal surfaces, and the corrosiveness of the oil determined by measuring the loss in Weight of the bearing at two hour intervals, up to ten hours. The tests apparatus comprises a stainless steel motor-driven spinner enclosing a copper-lead bearing specimen and a stationary stainless steel shaft connected to a base plate assembly. Copper baflies are also attached to the base plate assembly for the purposes of imparting turbulence to the oil and to act as oxidation catalysts. The bearing specimen is connected to the spinner by means of a special non-wearing bushing, so that the entire weight loss of the bearing is attributable to the corrosive action of the oil. The spinner enclosing the bearing specimen is immersed in a sample of the test oil maintained at 350 F. in a glass vessel and is rotated at a speed of 3000 revolutions per minute about the stainless steel stationary shaft. The oil is forced through the bearing clearance by capillary attraction and centrifugal force and is sprayed into the air through holes near the periphery of the rotating spinner. The following table shows results obtained by carrying out this test with a solvent-refined, dewaxed, Mid-Continent lubricating oil of S. A. E. 30 grade containing 1.0% of the phosphate ester-aldehyde condensation product described.

Corrosion test results The above table shows the substantial improvement in the corrosiveness of a mineral lubricating oil obtained by the addition of a small amount of a phosphorus compound of my invention.

In the standard Almen test for measuring the extreme pressure properties of lubricating compositions, a blend of 1.0% of this condensation product with the same base oil as described above, had an Almen value of 13 pounds, as compared with 9 pounds for the base oil alone.

According to the particular compound of this class selected, improvements in anticorrosiveness and extreme pressure properties, as well as other properties such as detergency and so forth which are exhibited by the phosphate esters generally, may be obtained in varying degrees.

Although a Mid-Continent parafiinic base lubricating oil was used in the example, the use of my compounds as lubricant additives is not limited to any particular base stock, since these compounds may be employed in mineral lubricating oil bases of a wide variety obtained from various types of crudes or synthetic oils by any of the conventional refining methods and also in other oleaginous materials such as animal or vegetable oils. Other compounding ingredients may also be present in the lubricant composition such as pour point depressors, oiliness agents, corrosion inhibitors, antioxidants, extreme pressure agents, viscosity index improving agents and thickening agents such as soaps either in minor amounts or in grease-forming proportions.

Obviously many modifications and variations of the invention as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A lubricant composition comprising a major amount of a mineral lubricating oil and about 0.1 to about 10 per cent by weight of a compound having the formula wherein X is a member of the group consisting of oxygen and sulfur, R is a member of the group consisting of hydrogen and aliphatic hydrocarbon groups containing from 1 to 6 carbon atoms, and R1, R2, R3 and R4 are aliphatic hydrocarbon substituted phenyl groups.

2. A lubricant composition comprising a major amount of a mineral lubricating oil and about 0.1 to about 10 per cent by weight of a compound having the formula wherein R is a member of the group consisting of hydrogen and aliphatic hydrocarbon groups containing from 1 to 6 carbon atoms and R1 is an aliphatic hydrocarbon group.

3. A lubricant composition comprising a major amount of a mineral lubricating oil and about 0.1 to about 10 per cent by weight of a compound having the formula CEHH (35 1: X 0 S S C? 5 1 \ll g l 35:

CEHU 5 ll Q W32 aHn CaHn References Cited in theme of this patent UNITED STATES PATENTS 2,531,129 Hook et a1. Nov. 21, 1950 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL AND ABOUT 0.1 TO ABOUT 10 PER CENT BY WEIGHT OF A COMPOUND HAVING THE FORMULA 